As a conventional permanent magnet embedded type rotor of this type, for example, the one disclosed in JP 2010-88219-A has been known.
A permanent magnet embedded type rotor disclosed in JP 2010-88219-A includes a rotor iron core that is formed by laminating electromagnetic steel sheets, a plurality of magnet insertion holes that are formed along the outer peripheral portion of the rotor iron core, and a plurality of permanent magnets that are embedded in the plurality of magnet insertion hole. Each magnet insertion hole is formed into a substantially C-shape as a whole, and both ends of each magnet insertion hole form air regions that bend to the radially inner side of the rotor iron core and the circumferentially end portions of which, where no permanent magnet exists, are formed into a circular arc shape. The air regions are configured to be arranged closer to the shaft hole side than the outer peripheral side surface of the permanent magnet and to extend to the shaft hole side beyond the inner peripheral side surface of the permanent magnet. Specifically, the circumferentially end portion of each air region is made up of a portion of a circular arc in contact with an outer peripheral side straight line portion of the magnet insertion hole, and the radially inner side end of each air region is made up of a portion of a circular arc that has a small radius and is in contact with a portion of the circular arc composing the circumferentially end portion.
The permanent magnet embedded type rotor disclosed in JP 2010-88219-A enables stress concentration due to centrifugal force in high-speed rotation to be relaxed.